Not sure if I posted any information on the 20 EXTREME on this site. It is a very versatile and efficient wildcat capable of running 32 to 55 grain .204 bullets to velocities achieved in cartridges from the 20 VarTarg to the 204R. It will do this with up to 22.2 grains of powder in Winchester 222 Rem brass formed to fit the chamber with the dies. A person, on another forum, was wanting to learn more about ways to work up loads so I posted the following.
To be sure there are many ways to work up loads and having a chronograph to check velocity and the ES & SD of your ladders is one good way that I have used. What we are looking for is consistency and a low ES, especially for longer range shooting. Having to develop loads for my wildcat rifles I have adopted a method using a multiple single load pressure ladder, starting low and working up in small increments to where I find potential stable loads. Usually there is a stable, low pressure, load just past where the base datum on the brass begins to expand. If you are using a chronograph this is usually indicated by an increase in velocity/ increment followed by little or no velocity increase / increment. Usually one of these has a low ES & SD. If measuring base datum expansion you will see a similar spike followed by little or no expansion. What I look for on the ladder target are 2-4 bullets that clump together and then use do a 3 shot, or more, ladder. There is usually another of these nodes as the pressures climb to where the primers start to flow, likely around 57-60000 PSI and another one just before the primers pierce and the brass does not spring back from the chamber, causing stiff bolt lift. If the primers hold past that and the action is very good many push the envelope to about 67,000 PSI where the primers defiantly begin to loosen.
For the last few years I have worked up many good loads that shoot sub 1/2 MOA in my 20 EXTREME. Until recently I have only run low pressure gopher loads in the 3470 -3550 fps range with the 39 & 40 grain bullets. The only faster load that I had run was the 40 V-Max with a 22.1 grains of Ramshot X-Terminator, a 96% load in Winchester brass. This load runs 3665 fps to 3722 on a hot day and at 25+Celcius is just beginning to run pressures that cause primer flow of 0.0025" with Rem 7 1/2 Primers. It is still not fire forming the brass at the base datum and the 0.0012" Spring Back or Chamber Clearance is near the max pressures I choose to run. I will attempt to show how I do this with the following.
Pressure ladder target in my 20 EXTREME LB with H 322:
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Pressure Ladder information for H 322:
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3 shot groups for #6,7 & 8 above:
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I did the same for the following and have a number of potentially good loads to follow up on.
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Confirmed RS X-Terminator load with 40 V-Max: Worked up in first 20 EXT.
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LT 32 and the 40 V-Max confirmed load in 20 EXT LB (worked up in first rifle
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These loads are all 90- 99 % load density and join the optimal powder, IMR 8208 that runs the 40 V-Max to near 3700 fps with a 100% load and minimum pressures as this chart shows.
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This chart shows the higher pressures generated with RL 10X that does well at 20.3- 20.5 with similar velocities but blows primers on hot days at the max listed load.
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To be sure there are many ways to work up loads and having a chronograph to check velocity and the ES & SD of your ladders is one good way that I have used. What we are looking for is consistency and a low ES, especially for longer range shooting. Having to develop loads for my wildcat rifles I have adopted a method using a multiple single load pressure ladder, starting low and working up in small increments to where I find potential stable loads. Usually there is a stable, low pressure, load just past where the base datum on the brass begins to expand. If you are using a chronograph this is usually indicated by an increase in velocity/ increment followed by little or no velocity increase / increment. Usually one of these has a low ES & SD. If measuring base datum expansion you will see a similar spike followed by little or no expansion. What I look for on the ladder target are 2-4 bullets that clump together and then use do a 3 shot, or more, ladder. There is usually another of these nodes as the pressures climb to where the primers start to flow, likely around 57-60000 PSI and another one just before the primers pierce and the brass does not spring back from the chamber, causing stiff bolt lift. If the primers hold past that and the action is very good many push the envelope to about 67,000 PSI where the primers defiantly begin to loosen.
For the last few years I have worked up many good loads that shoot sub 1/2 MOA in my 20 EXTREME. Until recently I have only run low pressure gopher loads in the 3470 -3550 fps range with the 39 & 40 grain bullets. The only faster load that I had run was the 40 V-Max with a 22.1 grains of Ramshot X-Terminator, a 96% load in Winchester brass. This load runs 3665 fps to 3722 on a hot day and at 25+Celcius is just beginning to run pressures that cause primer flow of 0.0025" with Rem 7 1/2 Primers. It is still not fire forming the brass at the base datum and the 0.0012" Spring Back or Chamber Clearance is near the max pressures I choose to run. I will attempt to show how I do this with the following.
Pressure ladder target in my 20 EXTREME LB with H 322:
Pressure Ladder information for H 322:
3 shot groups for #6,7 & 8 above:
I did the same for the following and have a number of potentially good loads to follow up on.
Confirmed RS X-Terminator load with 40 V-Max: Worked up in first 20 EXT.
LT 32 and the 40 V-Max confirmed load in 20 EXT LB (worked up in first rifle
These loads are all 90- 99 % load density and join the optimal powder, IMR 8208 that runs the 40 V-Max to near 3700 fps with a 100% load and minimum pressures as this chart shows.
This chart shows the higher pressures generated with RL 10X that does well at 20.3- 20.5 with similar velocities but blows primers on hot days at the max listed load.
